1. Field of the Invention
The present invention relates to tissue Doppler imaging (TDI), and more particularly, to a method and apparatus for obtaining Doppler images of tissue, which are captured using ultrasonic waves.
2. Description of the Related Art
An ultrasonic system is non-invasive and non-destructive, and thus is widely used in the medical field for obtaining information about the inside of a target object. An ultrasonic system provides high-resolution images of tissue inside a human body to medical doctors in real-time without the need of a surgical operation including direct incision and observation of the human body, and thus is used as an important device in the medical field.
An ultrasonic diagnosis apparatus transfers an ultrasonic wave signal from a body surface of a target object toward a predetermined portion in a body to obtain an image about a cross-section or hematoceles of soft tissue using information of the ultrasonic signal that is reflected by the tissue inside the body.
The ultrasonic diagnosis apparatus is compact, inexpensive, and is displayable in real-time. In addition, the ultrasonic diagnosis apparatus does not cause exposure to radiation, for example, X-rays, and is thus stable, and is widely used with other imaging diagnosis apparatuses such as an X-ray diagnosis apparatus, a computerized tomography (CT) scanner, a magnetic resonance imaging apparatus, or a nuclear medical diagnosis apparatus. Also, the ultrasonic diagnosis apparatus provides high-resolution images of the inside of a target object to medical doctors in real-time without a surgical operation including direct incision and observation of the target object, and thus is used as an important device in the medical field.
Hematoceles and myocardium react differently to ultrasonic waves. That is, hematoceles move far faster than myocardium but weakly reflect an ultrasonic wave. However, myocardium move slower than hematoceles but more strongly reflect an ultrasonic wave. Thus, when an ultrasonic signal reflected by hematoceles is removed from an ultrasonic response signal using these different characteristics, velocity of myocardial tissue may be measured. Evaluation of states of myocardium using the measured velocity of myocardial tissue refers to tissue Doppler imaging (TDI).
According to TDI, an identical sound field is transmitted to a scan line at predetermined time intervals to sense a variation in a phase of a received ultrasonic wave, and an average Doppler frequency is searched for simply by using auto-correlation, and a target object is displayed in a color image. Through the TDI, movement velocities of heart walls of a systolic period and a relaxation period may be objectively evaluated, and functional disorders of a heart may be examined for each portion of the heart, and a myocardium velocity may be quantitatively evaluated. Thus, TDI is very useful in tracking observation of a heart function regarding congenital and acquired heart diseases.